Thyroid Regulation

Thyroid Hormone Replacement

The most common treatment for low thyroid hormone levels consists of thyroid hormone replacement therapy. The goal of thyroid hormone replacement is to relieve symptoms and to provide sufficient thyroid hormone to decrease elevated TSH levels to within the normal range.87

Conventional treatment almost always begins with synthetic T4 (levothyroxine) preparations like Synthroid® or Levoyxl®. Low doses are usually used at first because a rapid increase in thyroid hormone may result in cardiac damage.88

Sometimes hypothyroid symptoms persist despite T4 treatment. In a 2001 study, T4 therapy was no more effective than placebo in improving cognitive function and psychological well-being in patients with symptoms of hypothyroidism, despite improvement in free T3 levels.89 A December 2010 study compared the T3 and T4 levels of hypothyroid patients treated with T4 alone against the levels found in healthy people and reported that T4 supplementation alone did not increase T3 to the same level as found in healthy people.90 As you will read later, deficiencies in nutrients like selenium can disable the body from converting T4 to biologically active T3.

In an animal study, rats with the thyroid gland removed were treated with T4 alone. The researchers found that no single dose restored normal concentrations of TSH, T4, and T3 in the blood, tissues and organs.91 The following year the same authors reported that a combination of T4 and T3 was able to normalize hormone levels in both blood and tissues.92 Other studies have failed to demonstrate any advantage of the combination therapy, although the results do suggest the possibility of a subset of hypothyroid patients who would benefit from combination therapy.93,94

One combination option is a drug called Thyrolar, which combines synthetic T3 and T4 in a fixed 1:4 ratio. Caution should be used, however, in administering T3 to older individuals because excess T3 may cause adverse cardiac events in this population.95

Another T3 option is a drug called Cytomel®, which is a synthetic form of T3. This can be used in combination with T4.

Desiccated Thyroid: Armour thyroid , Nature-throid, and Westhroid are prescription medications that contain desiccated porcine thyroid gland. Natural thyroid extracts have been used since 1892 and were approved by the Food and Drug Administration in 1939. Armour thyroid and most other natural glandular preparations are made to standards approved by the United States Pharmacopoeia.

Armour thyroid is preferred by some clinicians because it may achieve results in patients that fail to respond to levothyroxine alone. Patients with hypothyroidism show greater improvements in mood and brain function if they receive treatment with Armour thyroid rather than Synthroid®.96 One argument favoring natural hormones is that other naturally occurring hormones and chemicals found in these preparations may buffer or enhance the effect of the active hormones. 87,92

Ultimately, there may not be a single correct approach to low thyroid hormone levels. Instead, the best option may be to monitor thyroid levels through regular blood testing and systematically try various protocols to see what yields the best resolution of symptoms. Some people may prefer to begin with desiccated thyroid, while others may find it preferable to begin with T4 supplementation then move to a combination T3-T4 therapy if they experience no improvement from T4 alone.

Absorption of Thyroid hormone Medications: Coffee,97 aluminum antacids,98 ferrous sulfate (iron),99 calcium carbonate,100 soy 101 and possibly grapefruit juice102 can all decrease the absorption of thyroid hormone prescriptions. Most doctors simply advise patients to take thyroid away from any food or medication.

While most people take thyroid hormone in the morning, a December 2010 paper suggests that it is more effective to take thyroid just before bed.103

Nutrients to Support Thyroid Function

Iodine: The body needs iodine to make thyroid hormone. As of the late 1990s, thirty-two European countries were still affected by iodine deficiency.104 In 2007 the WHO estimated that over 30% of the world’s population (2 billion people) has insufficient iodine intake as measured by urinary iodine excretion below 100 micrograms (mcg)/liter.105 Iodized salt has proven to be effective at preventing iodine deficiency. The Morton Salt Company began selling iodized salt in the US in 1924.106

Hypothyroidism in the unborn child, congenital hypothyroidism or cretinism, is frequently caused by iodine deficiency. In industrialized countries the incidence is about 1 case in 4,500 live births. Yet, the incidence of cretinism can increase to as much as 1 case in 20 live births in areas that have iodine deficiency.107 Because of this, iodine deficiency remains one of the leading causes of mental retardation.108

During pregnancy T4 production doubles, causing increases in daily iodine requirements.109 Iodine deficient pregnant women cannot produce the thyroid hormones that are needed for proper neurological development of their growing babies, and are at high risk of giving birth to infants with cognitive impairment and learning delay. Even moderate iodine deficiency in a pregnant woman can lower her infant’s IQ from 8 to 16 points.110, 111

People who avoid iodized salt or adhere to a salt-restricted diet may become iodine deficient.112 Vegetarians are also at risk of developing iodine deficiency, especially if they eat food grown in low iodine soil.113 Vegans that avoid sea vegetables, are also at higher risk.114

Diets both low and high in iodine are associated with hypothyroidism. This is supported by studies that have shown that both low and high urinary iodine excretion are associated with hypothyroidism.115 High intake of iodine also increases the risk of Hashimoto’s thyroiditis.116

Iodine or foods high in iodine, such as seaweed, are thought useful in treating hypothyroidism but this is probably only true for people who are iodine deficient.113, 114 In 2007 Jane Teas reported a slight increase in TSH levels in healthy postmenopausal women who consumed 5 grams/day of seaweed (Alaria esculenta).117 A 2008 trial measuring the effect of eating Kombu (Laminaria japonica) seaweed in Japanese adults found that eating 15 and 30 grams of Kombu (containing 35 and 70 mg of iodine) daily for about a week, significantly increased TSH (which reflects lower thyroid hormone output).118

The upper intake level (UL) of iodine for adults is 1.1mg per day. The safety of therapeutic doses of iodine above the established upper intake level (UL) is evident in the lack of toxicity in people living in the northern coastal regions of Japan, whose diets contain large amounts of seaweed, have been found to have iodine intakes ranging from 50,000 to 80,000 mcg (50-80 mg) of iodine per day. 119 Studies using 3.0 to 6.0mg iodine per day to effectively treat fibrocystic breast disease may reveal an important role for iodine in maintaining normal breast tissue architecture and function. 120 Iodine may also have import antioxidant functions in breast tissue and other tissues that concentrate iodine. 121

Life Extension’s review of the scientific literature suggests an iodine intake up to 1,150 mcg daily is reasonable. However, the amount of supplemental iodine needed for an individual varies widely based on the factors listed above. It is important to test thyroid function when supplementing with iodine since both low and excessively high intake can contribute to hypothyroidism.

Selenium: After iodine, selenium is probably the next most important mineral affecting thyroid function. The thyroid contains more selenium by weight than any other organ.122 Selenium is a necessary component of the enzymes that remove iodine molecules from T4 converting it into T3; without selenium there would be no activation of thyroid hormone. When patients suffering from various forms of thyroid disease were tested for selenium levels, all were found to be lower than normal healthy people.123 Some researchers suggest that selenium supplementation will improve conversion of T4 to T3.124 Selenium also plays a role in protecting the thyroid gland itself. The cells of the thyroid generate hydrogen peroxide and use it to make thyroid hormone. Selenium protects the thyroid gland from the oxidative damage caused by these reactions. Without adequate selenium, high iodine levels lead to destruction of the thyroid gland cells.125, 126

People living in areas with low soil selenium content are more likely to develop Hashimoto's disease. 127 This may be because a selenium deficiency makes the enzyme glutathione peroxidase less effective. 128 Thus selenium supplementation has been suggested for treating Hashimoto’s disease.129

In a placebo controlled study published in 2002, researchers in Germany reported on an experiment in which they gave 200 mcg of sodium selenite daily to patients with Hashimoto's disease and high levels of thyroid peroxidase antibodies. After three months, the thyroid peroxidase antibody levels of the patients taking selenium were decreased by 66.4% compared to their pre-treatment values, and antibody levels returned to normal in nine of the selenium treated patients.130 Austrian researchers reported in 2008 that they were unable to duplicate the results of the earlier study when they did not limit the study population to those with high levels of thyroid peroxidase antibodies. They suggest that selenium supplementation might be of greater benefit to patients with higher disease activity. 131

Selenium deficiency is also common in celiac disease, and this may be the tie-in to increased frequency of thyroid problems with celiac disease.132

During severe or prolonged infection, blood levels of selenium, T4, T3 and TSH decrease and the conversion of T4 to T3 slows, inducing a hypothyroid state.133 Because the enzymes that moderate this conversion require selenium, it has been hypothesized that supplementing extra selenium might prevent this decrease in T3 during illness. Supplying extra selenium may decrease mortality from infection, but it does not normalize thyroid hormone levels.134 It seems that the suppression of T3 during sickness is mediated by cytokines, in particular interleukin-6 (IL-6).135 It may be that IL-6 and other cytokines, generated by the infection, limit production of the selenium-enzymes and interfere with hormone production.

Zinc: Zinc may be helpful in patients with low T3 and may contribute to conversion of T4 to T3. In animal studies, zinc deficiency lowered T3 and free T4 concentrations by approximately 30%. Levels of total T4 were not affected by zinc deficiency.136 In a group of patients with low levels of free T3 and normal T4, but elevated rT3 and mild to moderate Zn deficiency, taking oral zinc supplements for 12 months, normalized the serum free T3 and total T3 levels, decreased the rT3 and normalized TSH levels.137.

On the other hand, like iodine, too much zinc may suppress thyroid function.138 Very high doses of zinc interfere with copper absorption and can lead to serious and potentially fatal copper deficiency. 139., 140., 141. Thus it is advised to take copper when supplementing with zinc.

Iron: Iron deficiency hinders manufacture of thyroid hormone by reducing activity of the enzyme thyroid peroxidase. In one study 15.7% of women with subclinical hypothyroidism were iron deficient, compared to only 9.8 % of the control group.142 Iron-deficiency anemia decreases, and iron supplementation improves, the beneficial effects of iodine supplementation.143 Treating iron deficient hypothyroid patients with levothyroxine (T4) along with iron improves their iron deficiency anemia more than treatment with iron alone.144

Copper: An August 2010 study revealed that copper is important for normal brain development and its deficiency leaves the hypothalamus unable to regulate thyroid hormone effectively. Copper deficient pregnant rats give birth to infant rats that produce 48% less T3 than those born from healthy mothers.145

Vitamin E: Vitamin E may reduce the oxidative stress caused by hypothyroidism. In one animal study, vitamin E was shown to protect animals from increased oxidation and thyroid cell damage.146 In another study, vitamin E reduced the amount of thyroid cell replication in animals with induced hypothyroidism.147

Vitamin D: Deficiency of vitamin D may increase risk of autoimmune thyroid disease. When adjusted for age, presence of thyroid antibodies was inversely correlated with vitamin D levels in a group of 642 participants (244 males and 398 females) in New Delhi, India.148 Moreover, other evidence suggests that vitamin D deficiency is more common among individuals with thyroid cancer or thyroid nodules, compared to the general population.149 Given the many benefits of adequate vitamin D, it makes sense to supplement if needed.

Vitamin B12: Hypothyroid patients are often vitamin B12 deficient. In a 2008 paper, Pakistani doctors reported that of 116 hypothyroid patients tested for vitamin B12, approximately 40% were deficient.150 It isn’t clear what the link between B12 deficiency and low thyroid function is, nor if thyroid function will improve with B12 supplementation.151 But, since low B12 causes serious neurologic damage, all hypothyroid patients should be tested.

DHEA and Pregnenolone: Japanese researchers reported that concentrations of DHEA, DHEA-sulfate, and pregnenolone-sulfate are significantly lower in hypothyroid patients compared to age and sex matched healthy controls.152

Turmeric (Curcuma longa) Extract: A 2002 study, using rats, found that treatment with turmeric extract reduced the impact of chemically induced hypothyroidism in terms of thyroid weight, T4, T3 and cholesterol levels. 153 Results of a similar trial on rats treated with vitamin E and curcumin, a component found in turmeric, showed that treatment prevented a decline in basal body temperature and protected the liver.154

Rhodiola rosea: Given the fact that stress can influence thyroid status, it may be beneficial for some individuals with hypothyroidism to consider adaptogenic herbs such as Rhodiola.155, 156 Adaptogenic herbs support the adrenal glands and can improve the body’s response to stress.157

Dietary Recommendations

Some foods contain goitrogenic substances that reduce the utilization of iodine. These foods include canola oil, vegetables from the Brassica family (e.g., cabbage158 and brussels sprouts159), cassava160, and millet.161 The actual content of goitrogens in these foods is relatively low, however, and cooking significantly reduces the impact of these goitrogens on thyroid function.162

Studies show conflicting information concerning the impact of soy on the thyroid. Isoflavone molecules in soy do inhibit an enzyme involved in thyroid hormone synthesis,163,164 but that has not translated into poor thyroid function in otherwise healthy individuals with adequate iodine intake.165,166,167

For those with hypothyroidism, raw goitrogenic foods and soy foods that have not undergone fermentation and/ or food processing should be consumed in moderation and discontinued if symptoms should appear.